1. Field of the Invention
This invention relates to liquid manual dishwashing detergents, and more particularly, to such detergents which are gentle to the skin and combine high foaming power with high detergency.
2. Description of Related Art
Liquid cleaning preparations generally consist of aqueous solutions of synthetic anionic and/or nonionic surfactants and standard additives. They are used in particular for cleaning hard surfaces, for example, glass, ceramic materials, plastics, painted and polished surfaces. One important application for liquid cleaning preparations is in the manual washing of crockery and pots and pans. Dishwashing is normally carried out at moderately elevated temperatures of from about 35.degree. to 45.degree. C. in highly dilute cleaning solutions. The detergent power of a cleaning preparation is generally judged by the user to be better, the more vigorously and the longer the suds foam. Because the hands remain in contact with the washing suds for a prolonged period, the compatibility of the detergent with the skin is a particularly important factor in manual dishwashing. For these reasons, the artisan will be guided in the choice of the components and composition of a manual dishwashing detergent by other considerations than for liquid cleaning preparations for other hard surfaces.
It is generally known that alkylether sulfates, i.e., salts of sulfated adducts of from about 2 to 5 moles of ethylene oxide with fatty alcohols containing from about 10 to 18 carbon atoms, and preferably from 12 to 16 carbon atoms, in the aliphatic part, show high foaming and detergent power and are gentle to the skin. Accordingly, commercial manual dishwashing detergents are generally aqueous solutions of alkylether sulfates in conjunction with other surfactants, particularly alkylbenzene sulfonates, solution promoters, dyes and perfumes.
CH-PS No. 354,195 describes liquid manual dishwashing detergents containing a combination of an alkylether sulfate and a nonionic surfactant of the fatty acid-alkanolamide type of mono- or dialkanolamides with no more than 3 carbon atoms in each alkanol group of saturated C.sub.10 -C.sub.14 fatty acids together with water, solution promoters, dyes and perfumes.
It is also known from U.S. Pat. No. 3,219,656 that alkyl monoglucosides not only develop a stable foam themselves, but also act as foam stabilizers for other anionic and nonionic surfactants. They are said to be thusly comparable with and, in some cases, slightly better than the fatty acid alkanolamides. However, combinations with such alkanolamides are not described.
U.S. Pat. No. 3,925,224 describes detergency-boosting additives of basically water-insoluble or sparingly soluble surfactants to standard fabric detergents based on water-soluble surfactants. C.sub.8 to C.sub.24 fatty alcohol monoglucosides, inter alia, are proposed as suitable insoluble or sparingly soluble nonionic surfactants.
European Patent Application No. 70 076 describes foaming liquid detergents containing anionic surfactants, alkylglucosides and amine oxides or fatty acid alkanolamides, the alkylglucosides being alkyloligoglucosides containing the glucose unit about 1.5 to 10 times. This value is an average value and also takes into account the presence of alkylmonoglucosides in a corresponding proportion.
Alkylglucosides having a degree of oligomerization of higher than 2 are said to be particularly suitable.
3. Description of the Invention
It has now surprisingly been found that the foaming and detergent power of liquid detergents which are specifically designed for manual dishwashing and which contain synthetic anionic surfactants of the sulfonate and/or sulfate type, fatty acid alkanolamides and fatty alkylglucosides may be enhanced by selecting fatty alkylglucosides of the fatty alkylmonoglucoside type. In the context of the invention, fatty alkylmonoglucosides are understood to be compounds containing on average less than two glucose units per fatty alkyl group, more especially those containing from 1 to 1.4 glucose units. The fatty alkyl group contains from 10 to 18 carbon atoms and, in particular, essentially 12 to 14 carbon atoms. In the context of the invention, "fatty alkyls" are understood to be the residues of the fatty alcohols produced by hydrogenation of natural fatty acids, which are completely or predominantly saturated or which even contain unsaturated fractions.
Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about".
In one preferred combination, an alkylsulfate or an alkylether sulfate is used as the synthetic anionic surfactant. In the combination of these sulfate surfactants with the fatty acid alkanolamide and the fatty alkylmonoglucoside, the invention provides a detergent containing three different types of surfactants, wherein the hydrophobic part thereof is produced entirely from renewable fatty raw materials. In the case of the alkylglucosides, the hydrophilic part of the molecule also consists of a renewable raw material, i.e., sugar. In the preferred embodiment of the invention, therefore, anionic surfactants having a petrochemical base, particularly alkylbenzene sulfonate, are not used.
The alkylsulfates or alkylether sulfates preferably used are of the commercially available type and contain a linear aliphatic C.sub.12 -C.sub.18, and preferably C.sub.12 -C.sub.14 group. The associated cation is preferably an alkali metal or ammonium ion. In the case of the alkylether sulfates, the degree of ethoxylation is from 1 to 5 moles of ethylene oxide. The use of an alkylether sulfate mixture consisting of 50% by weight of a C.sub.12 alkylether sulfate and 50% by weight of a C.sub.14 alkylether sulfate containing from 1 to 5, and preferably from 2 to 4, moles of ethylene oxide instead of the alkylether sulfate mixture normally used which contains the same components in a ratio by weight of 70:30, is advantageous because it leads to a reduction in skin irritation without affecting the well-known high detergent power of these surfactants. Small additional quantities of alkylether sulfates containing less than 12 or more than 14 carbon atoms in the alkyl group have very little effect on these favorable results, but should nevertheless be avoided as far as possible.
The alkyl and alkylether sulfates are used in a quantity of from 2 to 25% by weight, and preferably in a quantity of from 3 to 20% by weight, based on the weight of the detergent.
The fatty acid alkanolamides used in the instant detergent contain a C.sub.8 -C.sub.18 and preferably C.sub.10 -C.sub.14 alkyl group in the fatty acid residue, while the amide group is substituted either by two C.sub.1 -C.sub.3 hydroxyalkyl groups, e.g., dialkanolamide or by one such hydroxyalkyl group and by one hydrogen or a C.sub.1 -C.sub.3 alkyl group. Mixtures of fatty acid monoalkanolamides and dialkanolamides are preferably used. These compounds are used in a quantity of from 1 to 15% by weight, and preferably in a quantity of from 1 to 5% by weight, based on the weight of the detergent.
the alkylmonoglucosides employed in accordance with this invention are used in quantities of from 2 to 25% by weight, and preferably in quantities of from 3 to 20% by weight based on the weight of the detergent as a whole, this quantity preferably being equal to or less than the combined quantity of sulfate surfactant and fatty acid alkanolamide. Suitable solution promoters, for example for dyes and perfume oils, include for example, alkanolamines, polyols, such as ethylene glycol, 1,2-propylene glycol, and glycerol, while suitable hydrotropes include alkali metal lower alkylbenzene sulfonates containing from 1 to 3 carbon atoms in the alkyl group, preferably sodium cumene sulfonate. They are used in quantities of from 3 to 15% by weight, based on the weight of the detergent as a whole.
In addition, solvents such as low molecular weight alkanols containing from 1 to 4 carbon atoms in the molecule, preferably ethanol and isopropyl alcohol, are generally used. These solvents are also used in quantities of from 3 to 15% by weight, based on the weight of the detergent as a whole. Thickeners, such as urea, sodium chloride, ammonium chloride and magnesium chloride may also be used herein either individually or in combination. Other standard optional additives include corrosion inhibitors, preservatives, dyes and perfume oils.
The remainder of the detergent composition to a total of 100% by weight comprises water.
In the following examples, the liquid detergents according to the invention were prepared by stirring the individual constituents together and allowing the mixture to stand until it is free from bubbles. The anionic surfactants used in the examples are the sodium salts thereof.